James s



y 24, 5 J. s. HELLEN 2,561,924

GUN SIGHT Filed Sept. 15, 1942 5 Sheets-Sheet l -LINE OF SIGHT- J. s. HELLEN 'GUN SIGHT July 24, 1951 Filed Sept. 15, 1942 5 Sheets-Sheet 2 y 1951 J15. HELLEN 2,561,924

GUN SIGHT Filed Sept. 15, 1942 5 Sheets-Sheet 5 July 24, 1951 J. s. HELLEN 2,561,924

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SPEED latented July 24, 1 951 UNITED STATES;

ecu SIGHG? James S; Hellen, Ramsey, N. J; assignor to Bendix Aviation. Gcrporation fiendix, N. J.,.a icorporaticn of Delaware Application September. 15, 1942, Serial No; 458,370.

' l The present invention relates to. gun sights, and. more particularly to a novel gun sight for machine guns or cannon mounted-onaircraft, in! cluding novel. means for compensating. ballistic: errors due to airspeed and altitude of the craft for'all directions of firingatany one ofaplurality of ranges of the target .to .be fired upon.

Heretofore, gun sights for. aircraft; machine gunsor cannon have been providedhaying. com pensating means for compensating-ballistic: .er:- rors due to airspeed of the craft fordifierentdirections of firing, but only at one fixed range, and no means were provided for compensating. ballistic errors due to changes in: a1titude-ofithe craft. See, for: example, the. patent to Robert Alkan, No. 2,183,530, dated December 19,- 1939.

Although. such sights as that disclosed; iii-the aforesaidAlkan patent adequately served. their. purpose and enabled the pilot or gunner to;-fire quiteaccurately at relatively low altitudesz.11p:to' possibly 3000feet and at a rangeof: about-A00. yards, they proved to be inadequatexatzranges: of 8.00 and mac-yards and atdifierentandrrelative- Zly higher altitudes between 3000 'and;27;0l)01feet at which modern. bombing aircraft fly. Accordingly, one of the objects. of the present finvention is 'to provide a novelIballisticallycome- ,pensated un sight for aircraft machine. gunsxor :cannon, whereby the inadequacies and: disade vantages of prior gun sights are overcome sot-as to provide much greater'accuracy of firing in any direction at any airspeed or altitude of; theainwraft and at any one 01" a pluralityof ranges o :the target.

Another object of the invention isto'providea "novel aircraft gun sight capable of automatically correcting, for any, direction of. firing, ballistic errorszdue to-the airspeedand;the'altitude:of the craft and at several diiferent rangesof-the target. Another object is to provide-in aniaircraft sight, novel means for producing the necessary aiming corrections of "the gun by compensating, at several difierentranges of. the target,.the-bal listicv errors, caused by the airspeed and thealtitudeof the craft on which the gun is mounted;

3, Claims (Cl. '.33f-49).

without changing the relative position of5thegun and elevation, including means for. correcting the. airmof. the gun for. ballistic errors by moving. an element such, for example, as thereticule of the. optical system of the sight, vertically and 1 laterally, in accordance with the angular movesightiof thecbllimatdr. typeadapted to be rigidly.

mounted on .thdgun, for angular movementas a unit therewith in azimuth and elevation, having an optical system .includingareticule and. means forfcrmingan image of saidreticule in the field of view in which the targetl is observed, and means. for-compensating. the ballistic errors due tothe airspeed and altitude of the aircraftby movingthe image. of .saidreticul in accordance withitheangular..movements ofthegun in azimuth and'elevation, andlmodifying. the move! ments ofisaidimag'e for. difierentranges of the target andffordifierent.airspeedsand altitudes of the aircraft, wherebythe aim of .the gun is madeaccurate regardless. of, the airspeed or altitude of the craft andflregardless.ofthe distance ofthe targetgfrom the craft withinv several predeterminediranges. I

.Astilljfurther object of ,the invention is to vpro-. vide' in an aircraftgun sight of'the classdee scribed; novel means v for compensating said sight for ballistic, errors dueto. the airspeed. and altitudeofgthei aircraft, at severaldifferent ranges offtheitarget; by moving the reticle ofthe sight verticallyandilaterally. with respect to-saidsight in-accordance withthe angularmovements ofthe gun .in azimuth -.and"el'evation, .modii ying the vertical ijandl lateral movements of "said. reticule for different airsp-eeds and altitudes of the aircraft, and further. modifying the vertical movemnt-ofsaid reticule for different ranges of the targetiandrior the. effects of gravity onv the bul leitonshell fired from the gun, .whereby. the aim otfthel, gun damade accurate regardless of air.- speed, altitude-.01 .range.

Theforegoing and otherobj ects and advantages....0f ith'e. invention. will appear more fully hereinafter. froma consideration of the detailed descriptien which. follows, taken together with theaccompanying. drawings wherein one embodimentof thejnventicnisiillustrated by way, of

Fig. 1 is a side view, in elevation, of an aircraft machine gun mounted in a universal gun mount for angular movement in azimuth and elevation"""""* and having the gun sight of the present inventionrigidly attached to the top thereof at the breech end;

Fig. 2 is a top plan view of the gun and gunsight shown in Fig. 1;

Fig. 3 is an end View of the gun and gun sight bearings 21, 28 for angular movement in elevation.

In accordance with the invention, means are provided for transmitting the movements of the gun in azimuth and elevation, i. e. about the vertical axis and the transverse horizontal axis, to the internal mechanism of the gun sight to obtain corresponding movement of the image of the reticule for-purposes ofcompensation, as will be explained hereinafter. In the form shown, said means comprise a pair of flexible shafts 29 and of acoupling 3| to a pinion 32 which meshes with and is driven by a gear 33 provided on the pe- -"riphery of platform 23 when the pinion 32 is platform 23.

of Fig. 1, as viewed from the right of thelatter figure and as seen by the gunner when firing the Fig; i is an enlarged side view, in elevation, ofthe gun sight of the invention without the gun,

and gun mount;

Fig. 5 is an enlarged top plan view of the sight shown inFig. 4;

Fig. 6 is an end view, in elevation, of the sight as viewed from the right hand end of Fig. 4;

Fig. '7 is another side view of the sight, in eleva tion, as viewed from the opposite side of that shown in Fig. 4;

Fig. 8 is another end view of the sight, in elevarange setting and re-setting portion thereof omitted;

Fig. 10 is another isometric view, also more or less diagrammatic, of the range setting and re setting mechanism of the sight;

Fig. 11 is a diagram showing the pivot points and fulcrums about which vertical and lateral movementof the reticule takes place to provide ballistic compensation of the sight in accordance with the present invention; and

Fig. 12 is an enlarged view of the reticule.

Referring now to the drawings, the gun sight, indicated in general by the reference numeral I2, is shown in Figs. 1, 2 and 3 as rigidly mounted on an aircraft machine gun l3 near the breech. thereof by means of bolts [4 and I5 'which'passi through lugs or ears I6 and I! of the casing 18' containing the internal mechanism of the gun,

sight. The gun I3 is provided with the usual grips or handles l9 and 20 by means of which'th'e gun is aimed and held in firing position when on the target, the firing button or trigger being shown at 2| and located between the grips l9 and 20 so that it may be easily actuated by the gunner by pressing his left or right thumb thereon while firmly holding the grips l9 and 20 with his'hands: and while observing the target through the eye-- piece 22 of the sight.

In order to provide for angular movement of the gun I3 in azimuth and elevation for aiming it at the target, the gun is mounted in a universal gun mount comprising a stationary horizontal circular platform 23 carried by a fixed support 24 which may be any fixed part of the aircraft on which the gun is carried. Mounted on the platform 23 for rotation thereon are a pair of spaced uprights or vertical arms 25, 26 which are adapted revolved about said gear 33 upon rotation of the gun I3 about the vertical axis on said horizontal The other end of flexible shaft 29 is connected bymeans of a coupling 34 to a driving shaft 35' (Fig. 9) of the internal mechanism of the gun sight I2. I

Shaft 30, on the other hand, is connected at one end by means of a coupling 36 to a bevel gear and bevel gear shaft (not shown) driven by the movementof. the? gun, l3 in elevation. The other end of shaft 30 is connected by means of a coupling 31 to a driving shaft 38 (Fig. 9) of the internal mechanism of the gun sight l2.

:Referring now to Fig. 9 of the drawings, the optical components and the internal mechanism, includingthe compensating means of the invention, comprise, as shown, a reticule consisting of a glass disc 39 attached to a vertically and laterally (horizontally) movable frame or carrier member 40; One side of said glass disc is first silvered and painted and then cross lines 4| and range circles Ma, 4117, Mo and Ma (Fig. 12) are. engraved on the treated surface so asto permit light rays from a suitable light source such as an.

electric lamp 42, after reflection by a reflector 43,

izontal direction and onto a reflecting surface such as a mirror 44 located in back of the reticule disc 39 just slightly below the reticule carrying frame'or carrier member 40.

The light rayswhich strike the reflecting surface- 44 are reflected vertically upward into a ,collimator lens 45 which forms an image 41 of the reticule lines 4| and projects it onto the undersideof a reflector'plate 46 made of suitable transparent. material such as polarized glass and placed in the line of sight of the observer so that thelatter. may view the target through said plate 46 and'at the same time see the image 41 of the reticule cross lines 43 in the same field of view in the eye piece 22. I The plate 46is mounted in a frame 48 attached to the top of the casing l8 of the gun sight in any suitable manner as by means of a pair of screws 49, 50, as shown in Figs. 4, -5 and '7. A rotatable polarized shade glass 5!, carried by a circular frame 52 pivoted at 53, is positioned ahead of the plate'46 in the path of the light rays coming from the'target so that the latter may be observed even when it is in the sun. Since the shade glass 5| is pivoted at 53 it may be lowered from the vertical position shown into a horizontal position parallel to the top ofthe casing [8 of the gun sight so as to be removed'from the line of sight when there is no sun to produce glare, as at'night, for example. i

As shown in Fig. 9, the reticule frame 40 is attached to or formed integrally with a tail piece 54 having rigidly attached thereto a shaft or rod 55lwhich' projects rearwardly of said tail piece; The projectingend'of said shaft'or rod 55 passes 3U, shaft 29 being connected at one end by means 52 through a sleeve 58 and is slidable therein; saidsleeve 56 being pivoted inside of another sleeve 51 about a vertical axis so that said tail piece 54 and'reticule frame 40 may move laterally in a horizontal direction to the left or'right of the initial position shown. The sleeve 51 is, in turn, pivoted inside of another member 58 about a horizontal axis represented by the screw 59, so that said tail piece Stand reticule frame 40' may move. vertically up and down about said axis 59; Thus, the sleeves 56, 57 and member 58'forlm a, universal mount providing a fulcrum point about which the frame 49 and, hence, the reticule: M maybe moved vertically and horizontally. i

Asshown in Figs. Qand 10, the member 59 is in the form ofa slide block mounted in a guide track- 69 formed" on the upper surface of a table- 6t which is also pivoted at one end on a pivot shaft 62' by means of a fork 93. attached to or formed integral-1y with the table. 6|. The pivot shaft 62' is attached at its ends to the casing of the gun sight and. is stationary, while the fork 63; and table 6] are adapted to rock about said stationary shaftasa pivot.

A vertical pin 64; is provided in and rigidly at.- tached to thetail piece it so as to project from the top; and bottom thereof, by means of w c vertical and lateral movement may be imparted. to the reticule frame ld and, therefore, to the reticule 41; about the fulcrumsformed :by the sleeves 5;,51andslideblock 58;.

In order to, obtain vertical movement of the rame ill nd; ret cule oss lines ll, the ottom, ofthe pin 6535, made to reston a lift plate 6,5 exendin r nsve s y o d under a r me i and carried at lt d e the e y on ndof a he t r re r; th her end- Q i h pass h i l eb a eeve Q lida le thereon and i to a block tfifinwhich said end is rigidly secured. The

lift plateGS projects-outwardly from the rod 69, in adireotion at right angles thereto, said rod constituting the solesupport for said lift plate.

The sleeve 61 is pivoted about a transverse-hon,- zontal. axis in. a vertical plate member 69 -moyae ble longitudinally of the shaft or rod 66 to providea shif-table fulcrum about which the lift plate Gamay.berockedverticallyup and downby a tu ating the rod 65. at itsother. -endby means ojf a. vertically movable bracket 19 within which, the b lgck'fifinis also'pivoted about a horizontal transverse axisin order to permit rocking movementlof,

Said rod 66 about the shiftabl'e fulcrumproyided by thepiyoted sleeve 61 and. platemember 69.

l The liftplatefij andthebottomv of the pinfi ii are maintained in engagement by means, of, a. itab e, rin no hown) u h as a c-shap d spring extending from thetop of the tailpiecefid around the end of the latter and under the lift plate, 6 5,

r In orderto obtain horizontal lateral movement,

ofthe reticuleframe 49 and, hence, of the reticule cross lines 4'! the top of the pin 64 is engaged by'a fork 'll formed inthe bottom of a reverseC- shaped laterally movable bracket 12 to the front side ofwhich is attached a plate 13; the lateral horizontal movement of said bracket 72 being guided'bymeans of a pair of'round rods or guides 14; l5projecting laterally from saidbracket and engaginga pair of upper guide rollers 16, wand;

As thealower guide roller 18, respectively. a frame tibismoved laterally by means of thepin along the top surface of-the-lift plate 65;

andbracket 12, the bottom of saidp' slides In accordance with the present inventiontuation'or the frame l -2 by means of the shaft 35 in accordance with the movement of the gun- [3 in azimuth to obtain the desired movement of the reticule cross-lines M in azimuth. To this end, the azimuth shaft 35, which is driven by flexible shaft 29 upon movement of the gun |3 in azimuth, has attached thereto a worm I 9 which meshes with and drives a worm gear to which is rigid-lysecureda driving and guide pin 9 I.

The worm gear 89 is journalled on a vertical shaft 82 which is permitted to pass freely through a central opening 83 in the gear in order that said shaftmay be moved axially up and down while-also-rotating, for a purpose which will presently: appear, and the drive and guide pin: 8| passes vertically downward through an opening M- provided in a. driven arm 85 rigidly: attachedto the vertical shaft 82 to rotate the latter by meansof said pin- 8| upon rotation of the wormgear Bllbythe worm 19 and azimuth-shaft The other end of shaft 82 is journalled-in aball bearing 86 contained in a vertical cylindrical member 81 attached to or formed integrallywith the bracket it, whereby thelatter may be moved up and down uponvertical movement of said shaft 92.- and at the same time permit rotation of said shaftin the ball bearing- 86.

Attached rigidly to and rotatable with the yertical shaft 82 is a so-called windage cam 88 which is eccentric of said shaft and bearsagainsta follower pin 99" attached to a vertically mov-- ableplateBll carried by a vertical threaded shaft 9| journalled in a rocking frame 92 pivoted on a horizontal shaft 93. The surface ofthe cam operating with a fixed index BBb-provided-at said opening.

Adjacent the vertically movable plate 99- is a second vertically movable plate 94 carried by another vertical; threaded shaft 95 which is also journalledin the rocking frame 92,said second plate 94 having a pin 96 attached thereto which bears against} the inner surface of the plate ii-'- carried by the: laterally -mo'vable bracket 1 2 The pin;- 96-- is maintained-- in engagement withthe plateli'l by means of a suitable spring 97 01119- end of whichisattached to the rocking frame; 92 and the other-end to the plate it.

It will-thus be seen that as thewormlgear H9 is rotated by the worm i9 and azimuth shaft- 35 inaccordance-- with the movement of the gun lfl in azimuth; the pin 9! rotates the arm-9ii-and shaft 82; thereby-- rotatingthe eccentric windage- 1 shaft -82 thereby rocking-the frame 92about the shaft 93; Since the frame 92 is resiliently'connected to plate 13; the latter will likewise be actuated laterally to move bracket 12 accordingly,

thereby moving'the reticule framedfitandreti cule cross-lines M laterally by meansof the for-1r ll-andpin 64-:

The: amount of lateral movement: of the-fol:- lower pin 89-bythe cam 88gfora given rise-oi" the-canr surface is; varied-in accordance with the-- vertical distance of saidpin 89 '-fromtheshaft 93 as determined by the amount of"rotation; of the vertical shaft 9 I, the rotation of which causes. vertical movement of the plate 90,.and, pin 89 longitudinally thereof. On the other hand, the amount of lateral movement of the bracket-12 bythe plate 13 and, hence, of the reticule frame 40, is varied in accordance with the vertical distance of ,pin 96 from the shaft 93 asdetermined by the amount of rotation of the vertical shaft 95, the rotation of which causes vertical movement of the plate 94 and pin 96 longitudinally thereof. a

; For the purpose of obtaining vertical movement of the reticule frame or carrier member 40 and of the reticule, M in accordance with the movement'of the gun I3in elevationfmeans are provided for actuating the lift plate 65 accordingly. To this end, the elevation shaft 38, which is driven by flexible shaft 30 upon movement of the gun in elevation, has attached thereto a worm 98 which meshes with a worm gear 99 secured to one end of a shaft I00, thereby rotating the latter. Also attached to said shaft I- at the other end thereof and rotatable therewith is a cylindrical elevation cam IOI which is eccentrically mounted on said shaft and arranged for rotation inside of a cam rider I 03 having an eccentric bore through which the cam IOI extends so that the cam rider may slide thereon longitudinally thereof by the action of a forked guide member I02, as will appear hereinafter, while said cam is being rotated in said cam rider by the shaft I00, said cam rider I03 being positioned between the two fingers of said forked guide member I02.

The cam rider I03 has on its under side a' knife edge which bears against a windage cam plate I04 to rock the latter about its trunnions I05, I06 against the tension of a spring I01, one end of which is fixed and the other end of which is attached to said windage cam plate. Thus, as the shaft I00 is rotated by the worm 98 and worm gear 99 upon angular movement of the gun I3 in elevation, the cam plate I04 is rocked. about its trunnions I05, I06 by the knife edge of the cam rider I03 by virtue of the rotation of the cam IOI in said cam rider due to the fact that said cam is eccentric of said shaft I00. The forked guide member I02 also has a threaded shaft I08 passing therethrough, which serves to cause longitudinal movement of said guide member and rider along the shaft I00 to vary the distance between the knife edge of the rider I03 and the pivot axis I05, I06 of the cam plate I04 for a purpose which will be described later.

This rocking movement of cam plate I04 is used to impart a lifting movement to the shaft 82 at the same time as the latter is rotated by means of worm I9 and worm gear 80 through the pin SI and arm 82. For this purpose, the arm 85 is provided with a roller I09 at its outer end so that said roller rolls over the surface of, the plate I04 as said arm rotates. If the plate I04 were always horizontal, no lifting of the shaft 82 would take place, but, as previously pointed out, said plate assumes various tilted positions about its trunnions I05, I06 due to its. actuation by the cam IOI through cam rider I03, Accordingly, when the cam plate I04 is tilted,v the arm 85 with its roller I09 will be lifted when the roller is rolling on the upwardly inclined portion of the cam plate and will be lowered when said roller is rolling on the downwardly ine clined portion of said cam plate. Since the arm 85 is attached to the shaft 82, the-1atter ;wi l llikewise be raised and lowered with said arm 35* the pin 64 since the latter rests on said lift plate 65.

\Means are also provided for modifying, the vertical movement of the reticule M to correct for the actionof gravity on the projectile fired by the gun. In the form shown, said means comprise a second and so-called gravity cam IIO which is also attached to the shaft I00 eccentrically thereof and is rotatable therewith inside of a block I I I having a central bore therethrough which is coaxial withthe shaft I00, whereby said block is caused to rise and fall by the action of the cam. IIO when the latter is rotated by the shaft I00.

Attached to the under side of said block III is a lift rod II2 which is curved at its lower end to form a hook II3 which engages a pin II4 provided at the bottom of the track table GI near the outer end of the latter for lifting said table to impart thereto arocking movement about its pivot shaft 62 upon vertical axial movement of said lift rod II2 due to its actuation by the gravity cam IIO. Thus, the track table GI and, hence, the slide block 58, is raised or lowered during rotation of the shaft I00 by the worm 98 and worm gear 99 during the elevation ordepression of the gun I3.

The lifting and lowering of the track table 6| about its pivot 62 causes a rocking movement of the tail rod 55 by means of the slide block 58 carried by said table and, therefore, a rocking movement of the reticule frame 40 since the latter is attached to the tail rod, with the pin 64 acting as a fulcrum for such movement, thereby causing a vertical movement of the reticule 4I in such a manner thatas the table 6| moves upward or downward, the reticule moves downward or upward, respectively, the extent of movement of the reticule being varied by varying the distance of the slide block 58 from the pin'64 for the purpose of correcting the gun sight for'different ranges of the target, as will be explained hereinafter.

Pursuant to the objects of the present invention, means are now provided for producing the necessary aiming corrections of the gun with the use of the gun sight of the invention, by compensating the sight, at several different ranges of the target, for the ballistic errors caused by the airspeed and altitude of the aircraft on which the gun is mounted, without changing the relative position of the gun sight with respectto the gun on which it is mounted, so that the aim of the gun, when the reticule is on the target,

Will be correct regardless of the airspeed or altitude of the aircraft or the distance of the target from the gun within several predetermined ranges. In accordance with the illustrated embodiment of the invention, such means are constituted by three separate adjusting means for performing the following respective functions:

.(1) Modifying the vertical and lateral movements of the reticule for different airspeeds of the aircraft;

(2) Modifying the-verticaland lateral movements, of. the reticule for diiferent altitudes of the aircraft; and

(3) Modifying the verticaland lateral move ments of the reticule for di'fie'rent ranges of the target. I

Referring again to Fig. 9 of the drawing, the means for modifying the vertical and lateral movements of the reticule for different airspeeds, and, therefore, of its image in the-fieldof viewJir'i which the target is observed, comprise, as shown, a manually rotatable knurledwheel or knob H5 secured to or formed integrally with athreaded shaft II-B engaging the vertical plate member. 69 in a threaded opening therein, whereby, upon manual rotation of said threaded shaft I I6 .by the knob H5, said plate member 69' will be moved longitudinally along rod 66 which carries thelift plate 65, to thereby shift the fulcrum formediby the horizontal transverse pivot axisof the sleeve 61. within said plat member 69. It will be apparent, by reference to Fig. 11, that such shifting shaft 82, thereby varying the vertical movement,

of-the lift plate 65 and, hence, of. thereticule frame 40 and reticule 4!, about said fulcrum, for a given vertical movement of they shaft 82 as determined by the amount of tilt offthe cam plate IM- caused by the cam I BI and cam rider I03 upon rotation of: the shaft I06 during movements of the gun inelevation.

Mounted on and rotatable with. the manually operated shaft H6 is a pinion II I which is drivably connected, either directl or through intermediate gears, to a worm gear II8 secured to the rotatable shaft 93 on which the frame 92 is pivoted; for rotating said shaft 93 simultaneously with the manual rotation of shaft I I6. This driving connection is shown diagrammatically in Fig.

9 bythe dotted line H9. The actual connection (not shown) between pinion I I1 and worm'geai' I I8 consists of a shaft having a worm at each end thereof and so arranged and located that one worm is engaged by pinion H1 and the other worm engages and drives worm gear I I8.

The worm gear II 8 meshes with and drives another worm gear I29 which is secured to the rotatable threaded shaft 95 for rotating the latter, thereby causing the plate 94 and pin 96 to move vertically up and down to vary the distance of said pin 96 from the shaft 93. It will be seen that this distance constitutes the lever arm for the point at which the pin 96 applies the lateral pivotal movement of the frame 92 to the plate I3 and bracket I2, and if the-lever arm is long, a greaterlateral movement will be imparted to the frame I2 and, hence, to the reticule frame III) and reticule 4|, than when said lever arm i short, for a given pivotal lateral movement of the frame 92 caused by the rotation of cam 88 and shaft/82 during angular movement of the gun in azimuth.- The longitudinal movement of the plate memher 69 along the rod 66 is calibrated in termsvof airspeed of the craft on which the gun and gun sight are mounted, 1. er, fora given airspeed, the plate member 69 is moved a certain predetermined amount and for another and different airspeed, said plate member is moved a different amount. The vertical movement of the plate. 95

and, pin 96 is also calibrated in like manner so that for different airspeeds, the pin 96 will be at different distances from the shaft 93. Theplate 94 and pin 96 move downward for increasing airspeed and upward for decreasing airspeed. The

1o airspeeds;-for which thecalibrations are made are indicated on, a fixed scale IZ'I by means of a suit,-

' able arrow I22" provided on the outer vertical edge of the plate member 69'. Inv the present embodiment, the calibrations are made for ai'rspeeds from 150 to 325 miles per hour.

The. manually operated wheel or knob H5 is made accessible .to.the pilot or gunner from the exterior of the casing I8 of'the gun sight, namely, on the left side. of the casing whenrthe operator is looking through the gun sight, as shown in Figs. 1,2, 3',. 5, 6, 7' and, 8-. Likewise, the scale I2I and pointer I22 are made visible from the exterior of the casing. on the same side thereof, as shown in Figs. 1 and 7.

Thus, the vertical, and lateral movements of the reti'cule. 4-I caused by movements of the guniin elevation and azimuth are modified for different airspeeds of the craft tocompensate for ballistic errors in elevation and azimuth produced at such airspeeds.

The means for further modifying the vertical and lateral movements of the-reticule for different, altitudes comprise, inv the form shown, a crank consisting of a manually operable handle I23 near the periphery of a wheel I24 attached to the threaded shaft I08. which, threadedly engages the cam rider I03, whereby, upon manual rotation of said threaded shaft I'Il8, the cam rider IE3 is caused to move longitudinally along said shaft and along the shaft I00 since rotation, of said rider with the shaft I08 is prevented by the shaft I00. Itwill be seen that th longitudinal movement of the cam rider I03 varies the distance. of the knife edge from the axis of trunnions I05, I I16 of the cam plate IM, thereby varyin the amount of tilt of said cam plate about its trunnions for agiven amount of vertical movement imparted to the cam rider I63 by thecam IIJI and shaft I06 duringangular movement of the gun in elevation. For example, if the knife edge is nearer the axis 05 thetrunnions, the tilt of the cam plate IM will be greater for a given vertical movement of the rider I03. by the camIIlI, than. when said knife edge is further away from said axis. i I Also attached toand rotatable with the manually operable threaded shaft is a pinion I 2.5 which is drivably connected, either directly or through intermediate gears, to a worm gear I26 provided on and secured to a sleeve I21 through which the shaft 93 passes freely, whereby said gear I26 is causedto rotate simultaneously with the rotation of pinion I25 upon manual actuation of the threaded, shaft I68 by the crank handle I23 and wheel I2 1. The driving connection between the pinion I25 and worm gear I26 iss hown diagrammatically by the dot-dash line I28. The actual connection (not shown) between pinion I25. and

worm gear I26 consistsofashaft havin a worm at each, endthereof and so arranged and: located that one worm engaged bypinion I25 and the other worm engages and drives worm gear I26.

-The worm gear I26 meshes with and drives another worm gear I29 which is secured to the vertical threaded shaft QI- for rotating thelatter, whereby vertical movement along said threaded shaft is imparted to the plate 911 and the follower pin 89 which rides on the-cam surface of the cam 88, rotation. of said plate-ill! by said shaft 9| beingprevented by means of; guides (not shown) formed on the side edges thereof. Pin 89 and platev 90 move downward for increasing altitude and upward for decreasing altitude.

1 From he for ing; it. will; be seen that the Ver "distance is greater. this lateral movement of theframe 92 is imparted 1'1 tical movement of the plate .90 and follower pin .89'along the threaded shaft 9| varies'the distance between said pin and the shaft 93011 which frame '92 is pivoted for lateral movement, said ditance being the lever arm of the point at which the lateral movement is imparted to said frame ,9 2 by the rotation of cam 88 and shaft 82 during angu lar movement of the gunin' azimuth. "Thus, for a given amount of rotationof cam 88, i..e., for a given position of the .gun' in azimuth, the amount of lateral movement of the frame 92 by the cam 88 will be greater when, the distance between the pin 89 and shaft'93'is shorter than when'said As previously pointed out,

to the frame 'IZthrough thepin 96 and plate I3 and, therefore, to'the reticule frame 40' and reticule M by means of the pin 64. f

The rotation of the threaded shafts I08 and BI is calibrated in terms of thousands of feet altitude sov that for a certain altitude the cam rider I03 and the pin 89 will be movedcertain predetermined amounts and for other altitudes said rider and pin will be moved correspondinglydifferent predetermined amounts to correct the ballistic errors produced at'such altitudes, 7 The The crank handle l23,,for manually rotating the shaft I08 is made accessible to the pilot or gunner from the exterior of thecasing I8 of the gun sight on the right hand side thereof when the pilot or gunner is looking through the sight,

as shown in Figs. 2, 3, 4, 5,6 andv 8. v t I Likewise, the'altitude'scale I and pointer'l3l are made visible from the exterior of the casing I8 of the gun sight at the left of the front end of the sight when the operator is at the eye-piece of said sight, as shown in Figs. 3, 5 and 8 of the drawings.

Thus, the vertical and lateral movements of the reticule 4I caused by movements of the gun in elevation and azimuth are-further modified for different altitudes of the aircraft to compensate for ballistic errors in elevation andazimuth produced at such altitudes." t

The means for still further-modifying the, vertical and lateral movements 'of the reticule for different rangesof the target are shown diagrammatically in Fig. 10. Asillustrated, said means comprise, in the form shown, a' wireor relatively thin cable I32 having one end attached toa rotatable drum I33 and its oppositeend ma second rotatable drum I34. "Both of said drums are biased by internal coil springs (not shown) and in angular directions such that when the wire or cable I32 is pulled to the right by hand, as'viewed in Fig. 10, the coil' spring"indrum I 33 will'be wound up and the one in'd i umi I 34 will become unwound, and when the manual pull on thejwire or cable I32 is released, the wound spring in drum I33 will automatically pullsaid wire to the left, thereby winding the cable on said "drum I33 and unwinding it from drum I34 while, at the same time, winding up the spring in drum I34., Also, the spring of drum I33 is madestronger than the spring of drum I34 .so that the latter acts merely as a take-up drum for taking up the slack in wire I32 as the latter is manually pulled to the right, while the drum I33 functions as a driving drum to pull the wire back to theleffi 12 when the manual pull thereon to the rightregleased.

The above-described action of the drums I33 and I34 is utilized to slide the range slide block 58 along its track 60 on the table 6| to varythe distance between the pin 64 and the fulcrum provided by the transversehorizontal pivot axis of sleeve 56 in the member 51, thereby varying the amount of vertical rocking movement of the reticuleiframe 40 and reticule 4| about the pin 64 as a fulcrum for a given amount of liftv of the table 6I by the hook II3 of the'lift rod II2 .during angular movement of the gun in elevation; and also varying the amount of both lateral and verticalmovements of the reticule frame about the fulcrums provided in the members 58 and 51. For this purpose, one or two turns of the wire or cable I32, intermediate the ends thereof, are wound around a pin I35 which projects from one side of the range slide block 58, so that when said wire or cable is manually pulled to theright against the tension of the coil spring of drum I33, said range slide block will be moved to the right along its track 60 and the slack in the wire will'be taken up by the take-up drum I34, and when the manual pull to the right is released, the range slide block will be moved to'the left by the force of the spring of drum I 33. The dis' tance between the pin 64 and the fulcrum pro vided by the transverse horizontal pivot axis of sleeve 56 in member 51 (distance X in Fig, 11)' is decreased for increased range and increased for decreased range.

In order to facilitate the manualmanipulation of the wire I32 for moving said range slide block 58, the pin I35 is arranged to be engaged by and between the ends of a forked member I36 which is pivotally mounted on a shaft I3! for angular movement thereon. Rigidly at-f tached to and rotatable with said shaft I31 is an arm I38 having a pin I39 at its end for engaging the forked member I36 when'said shaft is rotated. in a. counterclockwise direction, as viewedin Fig. 10, by means of a manually op; erable lever I49 attached to the other endof said shaft I31. A coil spring MI is provided for opposing the movement of .the arm -I38 upon rotation of the shaft I 31 by the manually opi erable lever I40, one end of said spring being fixed and its other end being attached'to the pin I39, so that when the lever is pulled to the right to actuate the arm I38 into engagement with the forked member I36 against the tension of said spring, the latter will pull said arm I38 away. from the forked member I33 after the lever I40 has been released. t

From the foregoing itwill be seen that as the manually operable lever I48 is pulled to the right, the range slide block 58 will be moved to the right along its track Bil against the pull of the spring of drum I33, and when the lever-isjrea leased, the pull of said spring will move the slide block 58 to the left.

Means are'provided for controlling the move ment of the range slide block 58 and to stop' it at predetermined points along the track fill' so that the amount of vertical and lateral move' mentof the reticule will be different at different positions of said slide block for the same increment of vertical movement'of the table 6| by the 1m; rod 2, and of the 1m; plate'GS b'y' I43 is shown as having four notches I-dfi; I41,

I48 and I45 along its inner edge for sequentially engaging the tail member I42 and stopping the block 58 as it is moved to the left by the spring of drum I33.

I-5I and E52 aligned in a' direction transversely of the length of said arm and arranged for successive engagement by a pawl I53 pivoted on one end of a bell-crank I514 which, in turn, is

pivoted at i5 5, the other end of said bell-crank having a pull-rod l-b't attached thereto for actuation of said pawl i553 and bell-crank I 55 against the tension of a spring Ilii' one end of which is fixed and its other attached to the bellcrank. A leaf spring 853 is also provided for biasing the pawl I53.

To operate the range setting mechanism, the lever I40 is manually pulled to the right as far as it will go, thereby moving the range slide block 58' against the pull of the spring of drum I33 until the tail member M2 of said slide block is engaged by the notch :43 of arm I 43. This position of the slide block represents the maximum range which, in the present instance, is 1800 yards. The lever Mii is then released, but the slide block will be held in its reset position by means of the arm I43. To move the slide block to the left to its next position to establish the next lower range of say 800 yards, the puil rod I56 is pulled to the right to actuate the bellcrank I54, which brings the pawl I53 into engagement with the notch 550 at the end of the arm I43 and pushes said arm away from the tail member I42 just enough to permit the slide block to move to the left by the action of drum I 33 until L the tail member I62 strikes the notch I41. The set range will now be 800 yards.

If the pull rod :55 is actuatedv two more successive times, the slide block will be moved to its next two successive positions represented by the notches i455 and M5 on the arm M3, said two positions representing, in the present instance, ranges of 509 and 400 yards, respectively,

The ranges for which the movement of the range block 58 is calibrated are indicated on a drum dial I53 attached to and rotatable with a shaft 16% to which the drum I36 is also attached.

The rangere-setting lever lib is made accessible to the pilot or gunner from the exterior of the casing I 8 of the gun sight on the right hand The other end of the notched arm I43 is provided with a set of three notches I 50,

side of said casing, as shown in Figs. 2, 3, 4, 5,

6 and 8.

The pull-rod I56 is also made accessible for actuation from the exterior of the casing at the lower left front of the latter, as shown in Figs. 1, 3, 7 and 8, and in order to facilitate the actuation of said pull-rod while thegun is held by means of the handles or grips I9 and 20, a bellcrank It! is provided which is pivoted at I62 and has one end thereof connected to the pullrod I56 (Figs. 1 and 7), the other end being arranged for actuation by pushing thereon with the thumb of the left hand by which the grip I9 is held.

The range drum I59 is also made visible from the exterior of the casing of the gun sight at the upper right hand corner of the front of the casing as {shown inFigs. 3, 5 and 8.

Thus, the'vertical and lateral movements of the reticule M caused by the angular movements or the gun in elevation and azimuth, are further modified in accordance with the range of the target to be fired upon, thereby correcting the ballistic errors regardless of the distance of thetargetfrom the gun within-certain predetermined ranges such-for example, as 400 yards, 600 yards, 800 yards and 1000 yards. i in order to stabilize the lateral and vertical movements of the reticule frame 4!] and reticule 41., the frame I2 has a vertical pin I63 attached thereto at the bottom thereof projecting down- 'wardly into a block Hi4 and slidably movable 'up'anddown therein, said block beingv attached to a rod I65 which slides at its ends 'inthe iirame 4B.

a clearer uuderstandingof what fulcrums are affected by movement of the airspeed slide 69 and range slide 553, reference is especiallymad'e to Fig. 11 wherein a: is the distance varied between pin '64 and the fulcrum within the slide block '58, :r' is the distance varied between pivot 6210f table bl and said fulcrum, and- 1 is the distance varied between the fulcrum in slide 69 and the gardl'ess of the direction of the target with re-.

spect to the aircraft or the distance of the target within several predetermined ranges. j Although only one embodiment of the invention has been illustrated and described by wayof example, various changes in the construction,

form and relative arrangement ofthe parts, which will now become apparent to those skilled in the art, may be made without departing from the scope of the invention. Reference is therefore.

to behad to the appended claims for a definition of the limits of the invention.

I I claim:

' i. Sighting-means for a gun mounted on an aircraft for movement in azimuth andi'n elevation, sighting means comprising an optical system including a reticule and means for forming an image of said reticule in the field of view in which the target is observed, an adjustable universal fulcrum, a carrier member carrying said reticule and pivotally mounted on said adjustable universal fulcrum for vertical and lateral horizontal rocking movements about said fulcrum to impart corresponding movements to said reticule, a pin attached to said carrier and extending above and below the same, laterally movable means engaging the top of said pin for moving said carrier laterally about said fulcrum, means responsive '1 to the movement of said gun in azimuth for actuthe bottom of the pin resting thereon, whereby vertical movement of said lift plate is imparted to said carrier and reticule, means responsive to the movement of said gun in elevation for actuating said lift plate, manually operable -ferent airspeeds of the aircraft and for HJQBQM .15 means for adjusting the fulcrum of said lift plate and for simultaneously adjusting the movement of said laterally movable means for different airspeeds of the aircraft, second manually operable means for adjusting the universal fulcrum of said reticule carrier for different ranges of the target, means responsive to the movement of said'gun in elevation for moving the universal fulcrum of said reticule carrier vertically and including means for modifying said movement for the effects of gravity on the projectile fired from said gun, and third manually operable means for adjusting the vertical movement of said lift plate and for simultaneously further adjusting the lateral movement of said laterally movable means for different altitudes" of said aircraft, whereby said reticule is moved laterally and vertically in coordination with the movement of said gun in azimuth and elevation and its movements are modified for different airspeeds and altitudes of the aircraft and for different ranges of the target. 2. Sighting means for a gun mounted on anaircraft for movement in azimuth and in elevation, said sighting means comprising an optical system including a reticule and means for forming an image of said reticule in the field of view means, a lift plate mounted on a second adjust-.

able fulcrum for vertical rocking movement about 'the same, said lift plate being positionedbeneath said carrier with the bottom of said pin resting thereon, whereby vertical movement of said lift plate is imparted to said carrier and'reticule, means responsive to the movement of said gun in elevation for actuating said lift plate, manually operable means for adjusting the fulcrum of said lift plate and for simultaneously adjusting the movement of the laterally movable means for different airspeeds of the aircraft, and second manually operable means for adjusting the universal fulcrum of said reticule carrier for different ranges of the target, whereby said reticule is moved laterally and vertically in coordination with the movement of said gun in azimuth and elevation and its movements are modified for difdifferent ranges of the target.

3. Sighting means for a gun mounted on an aircraft for movement in azimuth and in elevation, said sighting means comprising an optical system including a reticule and means for forming an image of said reticule in the field of view in which the target is observed, an adjustable universal fulcrum, a carrier member carrying said reticule and pivotally mounted on said adjustable universal fulcrum for vertical and lateral horizontal rocking movements about said fulcrum to impart corresponding movements tosaid reticule, a pin attached to said carrier and extending above and below the same, laterally movable means engaging the top of said pin for moving said carrier laterally about said fulcrum, means responsive to the movement of said gun in azimuth for actuating said laterally movable means, a lift plate mounted on a second adjustable fulcrum for vertical rocking movement about the same, said lift plate being positioned beneath said carrier with the bottom of said pin resting thereon, whereby vertical movement of said lift plate is imparted to said carrier and reticule, means responsive to the movement of said gun in elevation for actuating said lift plate, manually operable means for adjusting the fulcrum of said lift plate and for simultaneously adjusting the movement of the laterally movable means for different airspeeds of the aircraft, second manually operable means for adjusting the universal fulcrum of said reticule carrier for different rangesof the target, and third manually operable means for adjusting the vertical movement of said lift plate and for simultaneously further adjusting the lateral movement of said laterally movable means for different altitudes of said aircraft, whereby said reticule is moved laterally and vertically in coordination with the movement of said gun in azimuth and elevation, and its movements are modified for different airspeeds and altitudes of the aircraft and for different ranges of the target.

- JAMES S. HELLEN- REFERENCES CITED The following references are of'record in the file of this patent: g

UNITED STATES PATENTS 7 OTHER REFERENCES Coast Artillery Field Manual, pages 11 to 13,

vVol. II, Antiaircraft Artillery, Part2, Technique Certificate of Correction Patent No. 2,561,924 July 24, 1951 JAMES S. HELLEN It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 14, line 53, before sighting insert said and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 2nd day of October, A. D. 1951.

THOMAS F. MURPHY,

Assistant O'ommz'ssz'oner of Patents.

Certificate of Correction Patent No. 2,561,924 July 24, 1951 JAMES S. HELLEN It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1 1, line 53, before sighting insert said;

and that the said Letters Patent should be read as corrected ebove, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

